Containers for food storage are known. In many instances food storage containers are injection-molded which makes it possible to incorporate relatively complex molded-in features such as living hinges, freshness indicators and so forth. In this regard, see United States Patent Application Publication No. US 2004/0232026 of Goeking et al., entitled “Microwaveable Food Storage Container with Freshness Indicator and Steam Vent”.
A thermoformed food container is shown in U.S. Pat. No. 7,258,905 to Whitmore et al., entitled “Sealable Food Container With Improved Lidding and Stacking Features” which includes a base such as a plate or platter and a domed lid. While the lid and base include sealing features, it is apparent to one of skill in the art that a liquid-proof surface-to-surface, interference-fit seal is not readily achieved in connection with lidded thermoformed products because, in part, the base and lid are formed separately from different sheet stock in different forming tools. Gauge and mold variations as well as different forming parameters make tolerance control exceedingly difficult.
If a lid is too tight, the lid will either not easily fit the container base (if it fits at all), or when too much force is applied, crush the container; leading to extreme consumer frustration in either case. Accordingly, existing lidded thermoformed containers oftentimes have a base made of relatively heavy gauge material, while the lid is made of lighter sheet stock and the container is designed to have a relatively “light” capping force in order to avoid the foregoing problems as dimensional variation occurs during manufacturing. The seal thus has large tolerances and sealing of the container is severely compromised.
While liquid-proof and/or airtight seals are highly desirable, lightweight thermoformed containers are particularly difficult to lid tightly so that they are liquid-proof and/or airtight inasmuch as the capping force may crush the container unless heavyweight stock is used. See United States Patent Application Publication No. US 2007/0295721 of Van Handel et al., entitled “Sealable Portion Cups and Lids Therefor”.
Another desirable feature in single use and multi-use sealable container is a lid attached to the base or cup so that it is readily available and will not be misplaced. A problem with this arrangement is counter-top stability inasmuch as the weight of a lid tends to tip the container base. United States Patent Application Publication No. US 2003/0230582 of Whitmore et al., entitled “Separable Containers Arranged in Arrays With Integrally Formed Lids” shows thermoformed containers with hinged lids attached to cup portions. The hinge is a relatively stiff plastic hinge which lasts only a limited number of opening/closing cycles. Because of hinge stiffness, the hinge transmits torque due to the weight of the lid and makes a single container unstable on a counter-top as disclosed in the '582 publication. To ameliorate this problem, the product of the '582 publication is utilized in multi-container, separable arrays where the lids and cups are arranged so that the weight balances to make the arrays of containers counter-top stable; however, the arrangement is not adapted for using one container at a time as is frequently required.